To reliably predict a failure response of composite materials, ply level progressive failure analysis using material properties of the composite material may be used. Material properties of composite materials may be determined using standardized methodologies. For example, the ASTM D695-10 standard describes a methodology for testing the compressive property of rigid plastics. However, ply level progressive failure analysis tends to be sensitive to fiber direction material properties, and current standardized methodologies are not able to provide sufficiently reliable fiber direction material property information. For example, current test methodologies for measurement of fiber direction strength and strain tend to produce spurious failure modes leading to underestimation of critical compressive material properties.
Some causes of the spurious failure modes may be related to the manner in which composite test specimens are prepared. Composite test specimens used for compressive testing are typically prepared by bonding end tabs onto a sample of a material to be tested. The bonded end tabs can introduce problems, which may lead to premature failure of the composite test specimen. For example, the bonded ends tabs may lead to brooming of fibers. As a result, even with use of standard test methods, actual compressive failure limits of fibers of a composite test specimen may be underestimated. Additionally, spacing constraints (e.g., an amount of distance between the end tabs), may prevent performing direct strain measurements on the composite test specimen during testing. Accordingly, valuable information that could be gained by direct strain measurement is not available.